利用SBR实现自启动锁模钛宝石飞秒激光脉冲的产生

利用国内生长的低损耗双量子阱结构的可饱和布拉格反射器在掺钛蓝宝石激光器中实现了可饱和吸收体被动锁模、孤子锁模和KLM锁模状态的自启动稳定运转.当抽运功率为4.5W时，用啁啾镜进行色散补偿，获得了18fs的KLM锁模脉冲，输出功率为150mW. 关键词： 可饱和布拉格反射器 啁啾镜 飞秒 钛宝石激光器     

利用KTP晶体实现1.08μmNd：YAP激光器锁模

本文描述了利用ＫＴＰ晶体和腔的基波输出镜构成非线性镜实现１．０８μｍＮｄ：ＹＡＰ激光器的被动锁模。实验表明，这种新的锁模技术比用染料作可饱和吸收体的被动锁模技术有很多突出的优点，具有很大的发展潜力。实验测得锁模时基波１．０８μｍ输出２．４ｍＪ，二次谐波０．５４μｍ输出０．５ｍＪ（同样条件下的静态输出为２．５ｍＪ），基波脉冲的平均脉宽为４０ｐｓ。     

Passive stabilization of a passively mode-locked Nd:GdVO4 laser by inverse saturable absorption

A diode-pumped Nd:GdVO₄ laser mode-locked by a semiconductor saturable absorber and output coupler (SESAOC) is passively stabilized to suppress Q-switched mode-locking. A phase mismatched BIBO second-harmonic generation (SHG) crystal is used for passive stabilization. The continuous wave mode-locking (CWML) threshold is reduced and the pulse width is compressed. The pulse width is 6.5 ps as measured at the repetition rate of 128 MHz.     

Switchable mode-locking states in an all-fiber all-normal-dispersion ytterbium-doped laser

Multi-operation state in an all-normal-dispersion ytterbium-doped fiber laser is obtained by introducing nonlinear polarization or hybrid mode-locking mechanism in the laser cavity. In addition to operating the laser at continuous-wave mode-locking, various operation states including continuous-wave, Q-switched mode-locking, pulse-splitting, and harmonic mode-locking can be achieved by tuning the laser pump power or an intracavity polarization controller. Insertion of a semiconductor saturable absorber mirror in the cavity helps to shorten the output pulsewidth of the hybrid mode-locked laser. When the pump power is rapidly adjusted, a strong asymmetric hysteresis behavior can be observed during the manipulation between different orders of harmonic mode-locking.     

Mode-Locking Behaviour in Driven Colloids with Random Pinning

We find mode-locking steps in simulated force-velocity characteristics of external alternating-force （AF） driven colloids on a disordered substrate. Studies of mode-locking patterns in systems show that mode-locking steps are accompanied with the emergence of a dynamics phase： transverse solid phase. We also study the influence of temperature on the width of mode-locking steps. The mode-locked state is destroyed by thermal fluctuation and the width of mode-locking steps decreases rapidly with increasing temperature. In high velocity and low temperature regimes, due to the appearance of transverse solid phase and microscopically periodic velocity modulation, the step width changes little as temperature is varied.     

NAB对撞增强相位共轭腔快锁模特性

本文分析了NAB[NdAl_3(BO_3)_4]自激活激光晶体脉冲被动锁模的优越性。研究了对撞增强自起动自泵浦近简并四波混频相位共轭腔的形成条件及其在锁模过程中的作用。首次演示了NAB对撞增增强快速压缩脉冲锁模过程。获得了平均7ps的超短脉冲的实验结果。     

Gigahertz Harmonic Mode-Locked Fiber Laser Based on Tunable SMS Ultrafast Optical Switch

A novel passively gigahertz harmonic mode-locked all-fiber laser based on hybrid fiber structure (single-mode fiber–graded-index multimode fiber–single-mode fiber (SMS)) is proposed SMS, which coils on the paddles of polarization controller (PC), is demonstrated to modulate the temporal intensity for mode-locking. The nonlinear absorption properties of the optical switch are controllable by adjusting the paddles of PC; such an ultrafast optical switch enables the wavelength switchable harmonic mode-locking operation. Ultrafast pulses with 1.9 ps at 1558.41 nm and 0.95 ps at 1563.08 nm are generated. The maximum repetition rate of the laser up to 1.127 GHz harmonic of fundamental repetition mode-locking at 1563.08 nm, corresponding to 880 order, and the output power is 4.2 mW. Considering its superiority in terms of low cost, easy integration, and high reliability, the findings validate that SMS can be used in harmonic mode-locking.     

低阈值掺钛蓝宝石激光器实验研究

结合特殊的谐振腔设计和半导体可饱和吸收镜，建成了一台低阈值的自启动掺钛宝石激光器 . 分别用3％和12％的输出耦合镜，获得了阈值低至390mW和600mW的稳定锁模脉冲输出. 采 用12％输出耦合镜，在12W抽运时，输出平均功率为114mW，对应的典型脉宽为17fs，谱宽 为47nm. 相对于以往的低阈值克尔透镜锁模激光器，锁模工作的范围区域加宽，减小了操作 难度，提高了稳定性. 关键词： 低阈值 半导体可饱和吸收镜 克尔透镜锁模 掺钛蓝宝石激光器     

Passive mode locking at harmonics of the free spectral range of the intracavity filter in a fiber ring laser

We report the passive mode-locking at harmonics of the free spectral range (FSR) of the intracavity multi-channel filter in a fiber ring laser. The laser uses a sampled fiber Bragg grating (SFBG) with a free spectral range (FSR) of 0.8 nm, or 99 GHz at 1555 nm, and a length of highly nonlinear photonic crystal fiber with low and flat dispersion. Stable picosecond soliton pulse trains with twofold to sevenfold enhancement in the repetition rate, relative to the FSR of the SFBG, have been achieved. The passive mode-locking mechanism that is at play in this laser relies on a dissipative four-wave mixing process and switching of repetition rate is realized simply by adjustment of the intracavity polarization controllers.     

Ultrafast solid-state lasers

This article is intended to provide an introduction to ultrafast laser development for scientists new to the field and to provide a snapshot of the current state-of-the-art. In the first section, the main issues concerning ultrashort pulse generation are discussed and then the basic techniques of mode-locking are reviewed at a tutorial level. These include active mode-locking, passive mode-locking with real, resonant, saturable absorbers and passive mode-locking with the optical Ken effect. Emphasis is placed on practical ultrafast solid-state lasers for real-world applications.     

Synchronous Injection Locking Operation of Monolithic Diode Lasers Mode-Locked Diode Lasers

Synchronized mode-locking of monolithic mode-locked diode lasers has been demonstrated by injecting the light output from a master monolithic mode-locked diode laser. The master diode laser is a 10 GHZ hybridly mode-locked two section InGaASP quantum well laser. The slave lasers are a 10 GHz two section laser which is similar to the master laser, and a 20 GHz three section colliding pulse mode-locking laser. Both the slave lasers were greatly stabilized at 10 GHz frequency by a synchronous mode-locking mechanism under the injection of master laser pulses.     

Diode-pumped femtosecond Yb:CaNb2O6 laser

We report to our knowledge a diode-pumped passively mode-locked Yb:CaNb(2)O(6) (Yb:CN) laser for the first time. Both CW and passive mode-locking operation of the laser are experimentally investigated. A maximum CW output power of 1.4 W with a slope efficiency of 20% is obtained on a 7 mm long 1.5 at.% Yb:CN crystal, while stable passive mode-locking with a commercial semiconductor saturable absorption mirror (SESAM) was achieved on a 3 mm long 3 at.% Yb:CN crystal. The mode-locked pulses have pulse width of 251 fs and an average output power of 44 mW at 1038 nm.     

高能量掺Yb偏振型大模场面积光子晶体光纤孤子锁模飞秒激光器

实验研究了基于掺Yb偏振型大模场面积光子晶体光纤的孤子锁模激光器,获得了高脉冲能量的飞秒激光输出. 激光器基于线形腔结构,利用光栅对补偿腔内色散,并通过半导体可饱和吸收镜实现锁模的自启动. 实验中从振荡级直接获得了平均功率为700mW, 重复频率为47.3MHz(对应于14.8 nJ的单脉冲能量),脉冲宽度为518 fs的稳定锁模脉冲输出. 与普通孤子锁模飞秒光纤激光器相比,输出的单脉冲能量提高了两个数量级. 关键词： 光子晶体光纤 飞秒 光纤激光器 孤子锁模     

All-normal-dispersion Yb-doped mode-locked fibre laser and its stability analysis

We experimentally demonstrate an all-normal-dispersion Yb-doped mode-locked fibre laser with no intentional spectral filter inserted.Pulses with 1.1 nJ pulse energy at a repetition rate of 20.4 MHz are achieved.A theoretical model of the fibre laser is derived,whose coefficients are explicitly dependent on the orientations of the wave plates and the polarizer.Based on the model,stability diagrams of both the mode-locking and the continuous wave regimes of the laser are presented.The influence of group-velocity dispersion (GVD) and cavity length on the stability of mode-locking is also discussed.     

Diode-end-pumped passively mode-locked Nd:GGG laser with a semiconductor saturable mirror

We report on the passive mode-locking of a diode-end-pumped neodymium-doped gadolinium gallium garnet (Nd:GGG) crystal with a semiconductor saturable absorber mirror (SESAM). Continuous wave (CW) mode-locking was obtained. The mode-locked pulse duration was estimated to be ∼17.5 ps with a maximum average output power of 0.4 W. The mode-locked pulses have a repetition rate of 121.5 MHz. To our knowledge, this is the first demonstration of passive mode-locking of the diode pumped Nd:GGG lasers.     

Comparative study of the mode-locking of Nd:GdVO_4 and Nd:YAG lasers with semiconductor saturable absorber mirrors

Stable continuous-wave passive mode-locking of diode-end-pumped Nd:GdVO4 and Nd:YAG lasers with semiconductor saturable absorber mirrors (SESAMs) are reported. The comparative study shows that the Nd:GdVO4 crystal is efficient to decrease the Q-switched mode-locking tendency, and easier to continuous-wave (CW) mode lock than Nd:YAG.     

Er-doped all-fiber laser mode-locked by graphitic carbon nitride nanosheets

Few-layer graphitic carbon nitride(g-C_3N_4) nanosheets were fabricated and utilized as a saturable absorber for mode-locking in an Er-doped fiber laser with net normal dispersion. The g-C_3N_4/polyvinyl alcohol(PVA) hybrid-film-based saturable absorber has a modulation depth of 4.01% and a saturation intensity of 7.5 MW/cm~2. By integrating g-C_3N_4-PVA mode-locker into the laser cavity, a mode-locked operation could be obtained. The achieved mode-locking pulse centered at 1530.3 nm has a pulse width of 530 ps. Its repetition rate is 40.8 MHz, and the corresponding signal-to-noise ratio is about 55 dB.     

Generation of the numerator=2 rational harmonic mode-locked pulses in fiber ring lasers

In conventional rational harmonic mode-locking, optical pulse trains with the repetition rate of(pn + 1)fc are generated when the modulation frequency of the in-cavity modulator is set at fm=(n + 1/p)fc, where n and p are both integers, fc is the fundamental cavity frequency. In this paper, we report that rational harmonic mode locking phenomenon takes place in the fiber lasers when the modulation frequency is set at fm =(n + 2/p)fc. The pulse generations are experimentally demonstrated when the numerator of the rational corresponds to 2 in 5th and 7th order rational harmonic mode-locking.     

147 fs碳纳米管倏逝场锁模全光纤掺铒光纤激光器

利用化学腐蚀法在光纤包层表面成功制备了调制深度为3.9%的单壁碳纳米管饱和吸收体.组建了环形腔结构的全光纤掺铒光纤激光器,以制备的单壁碳纳米管薄膜为锁模元件,利用倏逝场锁模实现了锁模输出.锁模脉冲的中心波长为1556 nm,3 dB光谱带宽为24 nm,脉冲宽度为147 fs,重复频率为150 MHz.在520mW抽运功率下,平均输出功率为21 mW,相应的单脉冲能量为0.14 nJ.     

40 GHz Mode-Locked Semiconductor Lasers: Theory, Simulations and Experiment

We study both theoretically and experimentally typical operation regimes of 40 GHz monolithic mode-locked lasers. The underlying Traveling Wave Equation model reveals quantitative agreement for characteristics of the fundamental mode-locking as pulse width and repetition frequency tuning, as well as qualitative agreement with the experiments for other dynamic regimes. Especially the appearance of stable harmonic mode-locking at 80 GHz has been predicted theoretically and confirmed by measurements. Furthermore, we derive and apply a simplified Delay-Differential-Equation model which guides us to a qualitative analysis of bifurcations responsible for the appearance and the breakup of different mode-locking regimes. Higher harmonics of mode-locking are predicted by this model as well.